482 SCIENTIFIC RECORD FOR 1885. 



slow wave-like motion. (Compt. Eend., c: 758.) The work of this obser- 

 vatory is also described in La Nature (i: 363), and illustrated by speci- 

 mens of the daily maps issued by the observatory. The maps given are 

 those illustrating the phenomena of the earthquake which occurred near 

 Modena on February 26, 1885. 



The work of the Swiss Seismological Commission, from its appoint- 

 ment in 1879, is summarized by W. M. Davis in Science (V : 196). Among 

 other things there will be found here the statement of the scale of 

 intensity adopted by the Italian and Swiss observers, and commonly 

 known as the Eossi-Forel scale. In forming a number to represent 

 the "value" of an earthquake, it is necessary to combine with the 

 intensity-scale number others to represent the area affected and the 

 number of accessory shocks. For Switzerland the areas are grouped 

 by diameters of 5, 50, 100, and 150 kilometers, and the weak, medium, 

 and strong shocks are reckoned separately (n, n', n"); then the adopted 

 value is V= (intensity scale x area scale) -f n + 2n' + 3n". Professor 

 Davis thinks this formula would be improved by squaring the intensity 

 number to offset the much greater intervals between the upper numbers 

 of that scale. {Science, v: 197.) 



The third report of the Swiss Seismological Commission, by Forel, 

 covers the years 1883 and 1883. It gives a detailed list of the earth- • 

 quakes observed during the two years, with the accessory shocks. The 

 intensity of each earthquake is marked according to the Eossi-Forel 

 scale, and its " value" computed by the formula mentioned above. These 

 numbers are tabulated and compared with the mean of the two years 

 1880 and 1881, and with the separate numbers for those years. From 

 the results the author infers that there was a maximum of seismic 

 activity in Switzerland in 1881, which a comparison of the monthly 

 values shows to have been in November of that year, and that in 1882 

 and 1883 the activity was notably diminished. This was especially so 

 in the latter year, in which no earthquake "value" reached even the 

 average value for 1881, and the mean "value" for 1883 scarcely exceeded 

 one-third of the mean value for 1881. {Arch, des Sci., Phys., et Nat, xiii: 

 377.) 



M. Montessus, in transmitting to the French Academy his work on 

 Central American Earthquakes, published in San Salvador, states that 

 he entered upon the work and collected a large amount of material 

 with the purpose of formulating, if possible, the rules by which tbe in- 

 habitants, apparently from meteorological considerations, announce in 

 advance the occurrence of an earthquake. He was, however, soon con- 

 vinced that the connection between earthquakes and meteorological 

 phenomena, if any, is not yet sufiBciently understood to base predictions 

 upon it, although a hope is expressed that the further study of material 

 collected may give some results. {Compt. Rend., C: 1312.) 



Commenting upon the not infrequent observation that earthquake 

 shocks are felt more severely at the surface of the earth than in mines, 



